1. Field of the Invention
The present invention relates generally to a new and improved syringe for drawing blood that helps to address the problem of drawing blood from patients who have small veins or veins which collapse. Many of these patients are children who may not be entirely cooperative during blood drawing procedures. Therefore, my new and improved syringe allows for blood to be drawn into multiple tubes without removing the needle from the vein. In addition, the syringe also minimizes the risk to the person doing the venipuncture for accidental "needle sticks" and exposure to infectious diseases. The present invention also provides a check valve within the syringe to prevent return of drawn blood or backflow of testing solutions (chemicals) into the bloodstream of the patient.
2. Description of the Prior Art
Over the past few years, especially since AIDS has been described, there has been a number of changes to the basic design of syringes and needles in an attempt to minimize accidental "needle sticks" and the possible transfer of infectious agents. Most of these designs have focused on ways to automatically sheath the needle after the blood is drawn.
In addition, over the past decade, there have been methods developed to facilitate the way in which multiple tubes of blood can be collected following a single venipuncture. Primarily this has been done by the use of a system involving Vacutainer.RTM. tubes which, unfortunately, tend to collapse small or weak-walled veins because of the vacuum being applied to the veins.
Other types of syringes that could allow for multiple tubes of blood include syringes with three-way stopcocks coupled to syringes in order to do venipuncture in such a way that appropriate suction could be applied to pull out blood from a vein without collapsing it. During the venipuncture procedure, by intermittently switching the valve on the stopcock, multiple sample tubes could be filled. This technique, however, is much less the satisfactory because of all the movement involved which would usually cause the needle to come out of the vein, especially in a patient who was not completely motionless.
As blood is drawn from a patient with weak or small veins, the punctured vein may begin to collapse. At that point it is common to stop pulling on the plunger of the syringe and possibly even push the plunger partially back into the syringe to try and keep the vein from collapsing, however, this technique is not possible if the syringe already contains a solution, such as a testing solution, since this solution can cause serious damage or even death to the patient. It is therefore desirable to provide a syringe that can also prohibit the backflow of drawn blood back into the vein of a patient.
Certain U.S. patents are peripherally related to the problem, but none show the structural promise needed for an instrument usable in the wide area of applications addressed herein. These prior approaches are given representatively in the following Topham U.S. Pat. No. 3,957,052; Hughes U.S. Pat. No. 3,557,778; and Brannon U.S. Pat. No. 5,147,329.
There have been various types of syringes developed and made available in the marketplace, but none have been able to provide for an inexpensive multiple-draw, variable suction syringe as is disclosed herein. Furthermore, none of the prior art syringes provide for a syringe that addresses the problem of drawing blood from patients who have small veins or veins that easily collapse, that can allow for easy withdrawal of multiple tubes of blood, and that allow for a minimal amount of "needle sticks". Other types of syringes disclosed in the prior art do not offer the flexibility and inventive features of my convenient and easy-to-use syringe. As will be described in greater detail hereinafter, the multiple-draw, variable suction syringe of the present invention differs significantly from those previously proposed.